The present invention relates generally to characterizing a patient's propensity for a future neurological event and communicating with the patient. More specifically, the present invention relates to characterizing a propensity for a future seizure and when it is determined that the patient has a high or elevated propensity for a seizure, providing a communication to the patient that is indicative of an appropriate action for responding to the patient's elevated propensity for the seizure. Optionally, such information may be incorporated into an interactive communication protocol in order to convey appropriate communications, such as instructions or recommendations to the patient and receive historical and real-time patient status information and acknowledgements associated with the management of the patient's care.
Epilepsy is a disorder of the brain characterized by chronic, recurring seizures. Seizures are a result of uncontrolled discharges of electrical activity in the brain. A seizure typically manifests as sudden, involuntary, disruptive, and often destructive sensory, motor, and cognitive phenomena. Seizures are frequently associated with physical harm to the body (e.g., tongue biting, limb breakage, and burns), a complete loss of consciousness, and incontinence. A typical seizure, for example, might begin as spontaneous shaking of an arm or leg and progress over seconds or minutes to rhythmic movement of the entire body, loss of consciousness, and voiding of urine or stool.
A single seizure most often does not cause significant morbidity or mortality, but severe or recurring seizures (epilepsy) results in major medical, social, and economic consequences. Epilepsy is most often diagnosed in children and young adults, making the long-term medical and societal burden severe for this population of patients. People with uncontrolled epilepsy are often significantly limited in their ability to work in many industries and cannot legally drive an automobile. An uncommon, but potentially lethal form of seizure is called status epilepticus; in which a seizure continues for more than 30 minutes. This continuous seizure activity may lead to permanent brain damage, and can be lethal if untreated.
While the exact cause of epilepsy is uncertain, epilepsy can result from head trauma (such as from a car accident or a fall), infection (such as meningitis), or from neoplastic, vascular or developmental abnormalities of the brain. Most epilepsy, especially most forms that are resistant to treatment (i.e., refractory), are idiopathic or of unknown causes, and is generally presumed to be an inherited genetic disorder. Demographic studies have estimated the prevalence of epilepsy at approximately 1% of the population, or roughly 2.5 million individuals in the United States alone. Approximately 60% of these patients have epilepsy where specific focus can be identified in the brain and are therefore candidates for some form of a focal treatment approach.
In order to assess possible causes and to guide treatment, epileptologists (both neurologists and neurosurgeons) typically evaluate people with seizures with brain wave electrical analysis (e.g., electroencephalography or “EEG” and electrocorticograrri “ECoG”, which are hereinafter referred to collectively as “EEG”) and imaging studies, such as magnetic resonance imaging (MRI). While there is no known cure for epilepsy, chronic usage of anticonvulsant and antiepileptic medications can control seizures in most people. The anticonvulsant and antiepileptic medications do not actually correct the underlying conditions that cause seizures. Instead, the anticonvulsant and antiepileptic medications manage the patient's epilepsy by reducing the frequency of seizures. There are a variety of classes of antiepileptic drugs (AEDs), each acting by a distinct mechanism or set of mechanisms.
For most cases of epilepsy, the disease is chronic and requires chronic medications for treatment. AEDs generally suppress neural activity by a variety of mechanisms, including altering the activity of cell membrane ion channels and the propensity of action potentials or bursts of action potentials to be generated. These desired therapeutic effects are often accompanied by the undesired side effect of sedation. Some of the fast acting AEDs, such as benzodiazepine, are also primarily used as sedatives. Other medications have significant non-neurological side effects, such as gingival hyperplasia, a cosmetically undesirable overgrowth of the gums, and/or a thickening of the skull, as occurs with phenyloin. While chronic usage of AEDs has proven to be effective for a majority of patients suffering from epilepsy, the persistent side effects can cause a significant impairment to a patient's quality of life. Furthermore, about 30% of epileptic patients are refractory (e.g., non-responsive) to the conventional chronic AED regimens. This creates a scenario in which over 500,000 patients in the United States alone have uncontrolled epilepsy.
If a patient is refractory to treatment with chronic usage of medications, surgical treatment options may be considered. If an identifiable seizure focus is found in an accessible region of the brain, which does not involve “eloquent cortex” or other critical regions of the brain, then resection is considered. If no focus is identifiable, or there are multiple foci, or the foci are in surgically inaccessible regions or involve eloquent cortex, then surgery is less likely to be successful or may not be indicated. Surgery is effective in more than half of the cases in which it is indicated, but it is not without risk, and it is irreversible. Because of the inherent surgical risks and the potentially significant neurological sequelae from resective procedures, many patients or their parents decline this therapeutic modality.
Some non-resective functional procedures, such as corpus callosotomy and subpial transection, sever white matter pathways without removing tissue. The objective of these surgical procedures is to interrupt pathways that mediate spread of seizure activity. These functional disconnection procedures can also be quite invasive and may be less effective than resection.
An alternative treatment for epilepsy that has demonstrated some utility is Vagus Nerve Stimulation (VNS). This is a reversible procedure which introduces an electronic device which employs a pulse generator and an electrode to alter neural activity. The vagus nerve is a major nerve pathway that emanates from the brainstem and passes through the neck to control visceral function in the thorax and abdomen. VNS uses intermittent stimulation of the vagus nerve in the neck in an attempt to reduce the frequency and intensity of seizures. See Fisher et al., “Reassessment: Vagus nerve stimulation for epilepsy, A report of the Therapeutics and Technology Assessment Subcommittee of the American Academy of Neurology,” Neurology 1999; 53:666-669. While not highly effective, it has been estimated that VNS reduces seizures by an average of approximately 50% in about 50% of patients who are implanted with the device.
Another recent alternative electrical stimulation therapy for the treatment of epilepsy is deep brain stimulation (DBS). Open-loop deep brain stimulation has been attempted at several anatomical target sites, including the anterior nucleus of the thalamus, the centromedian nucleus of the thalamus, and the hippocampus. The results have shown some potential to reduce seizure frequency, but the efficacy leaves much room for improvement.
There have also been a number of attempts described in the patent literature regarding the use of predictive algorithms that purportedly can predict the onset of a seizure. When the predictive algorithm predicts the onset of a seizure, some type of warning is provided to the patient regarding the oncoming seizure. For example, see U.S. Pat. No. 3,863,625 to Viglione and U.S. Pat. No. 6,658,287 to Litt et al.
While conventional treatments for epilepsy have had some success, improvements are still needed.